In a joint, the range of motion depends upon the anatomy and condition of that joint and on the particular genetics of each individual. Many joints primarily move either in flexion or extension, although some joints also are capable of rotational movement in varying degrees. Flexion is to bend the joint and extension is to straighten the joint; however, in the orthopedic convention some joints only flex. Some joints, such as the knee, may exhibit a slight internal or external rotation during flexion or extension. Other joints, such as the elbow or shoulder, not only flex and extend but also exhibit more rotational range of motion, which allows them to move in multiple planes. The elbow joint, for instance, is capable of supination and pronation, which is rotation of the hand about the longitudinal axis of the forearm placing the palm up or the palm down. Likewise, the shoulder is capable of a combination of movements, such as abduction, internal rotation, external rotation, flexion and extension.
Most people do not appreciate the complexity of joint motion until something goes wrong, such as when an injury results in lost range of motion. When a joint is injured, either by trauma or by surgery, scar tissue can form or tissue can contract and consequently limit the range of motion of the joint. For example, adhesions can form between tissues and the muscle can contract itself with permanent muscle contracture or tissue hypertrophy such as capsular tissue or skin tissue. Lost range of motion may also result from trauma, such as excessive temperature (e.g., thermal or chemical burns), or surgical trauma, so that tissue planes which normally glide across each other may become adhered together, markedly restricting motion. The adhered tissues may result from chemical bonds, tissue hypertrophy, proteins such as Actin or Myosin in the tissue, or simply from bleeding and immobilization. It is often possible to mediate, and possibly even correct this condition by use of a range-of-motion (ROM) orthosis, but the longer the period of stiffness or loss of motion the greater the time interval and the force required to regain lost range of motion. Therefore, it is beneficial to treat the tissue or joint as early as possible. For example, a ROM orthosis may be applied immediately after surgery or as soon as the stiffness problem is diagnosed.
ROM orthoses are used during physical rehabilitative therapy to increase the range-of-motion of a joint. Additionally, they also may be used for tissue transport, bone lengthening, stretching of skin or other tissue, tissue fascia, and the like. When used to treat a joint, the device typically is attached on opposite members of the joint so that is can apply a force to move the joint in opposition to the contraction.
A number of different configurations and protocols may be used to increase the range of motion of a joint. For example, stress relaxation techniques may be used to apply variable forces to the joint or tissue while in a constant position. “Stress relaxation” is the reduction of forces, over time, in a material that is stretched and held at a constant length. Relaxation occurs because of the realignment of fibers and elongation of the material when the tissue is held at a fixed position over time. Treatment methods that use stress relaxation are serial casting and static splinting. One example of devices utilizing stress relaxation is the Joint Active System, which uses a rack and pinion gear to move and hold the joint in a constant position.
Sequential application of stress relaxation techniques, also known as Static Progressive Stretch (“SPS”) uses the biomechanical principles of stress relaxation to restore range of motion (ROM) in joint contractures. SPS is the incremental application of stress relaxation—stretch to position to allow tissue forces to drop as tissues stretch, and then stretching the tissue further by moving the device to a new position—repeated application of constant displacement with variable force. In an SPS protocol, the patient is fitted with an orthosis about the joint. The orthosis is operated to stretch the joint until there is tissue/muscle resistance. The orthosis maintains the joint in this position for a set time period, for example five minutes, allowing for stress relaxation. The orthosis is then operated to incrementally increase the stretch in the tissue and again held in position for the set time period. The process of incrementally increasing the stretch in the tissue is continued, with the pattern being repeated for a maximum total session time, for example 30 minutes. The protocol can be progressed by increasing the time period, total treatment time, or with the addition of sessions per day. Additionally, the applied force may also be increased.
Exemplary orthoses that utilize the stress relaxation and/or SPS protocols include, but are not limited to, those described in U.S. Pat. No. 6,921,377 (“Finger Orthosis”), U.S. Pat. No. 6,770,047 (“Method of using a neck brace”), U.S. Pat. No. 6,599,263 (“Shoulder Orthosis”), U.S. Pat. No. 6,113,562 (“Shoulder Orthosis”), 6,503,213 (“Method of using a neck brace”), U.S. Pat. No. 6,502,577 (“Finger Orthosis”), U.S. Pat. No. 5,848,979 (“Orthosis”), U.S. Pat. No. 5,685,830 (“Adjustable Orthosis Having One-Piece Connector Section for Flexing”), U.S. Pat. No. 5,611,764 (“Method of Increasing Range of Motion”), U.S. Pat. No. 5,503,619 (“Orthosis for Bending Wrists”), U.S. Pat. No. 5,456,268 (“Adjustable Orthosis”), 5,453,075 (“Orthosis with Distraction through Range of Motion”), U.S. Pat. No. 5,395,303 (“Orthosis with Distraction through Range of Motion”), U.S. Pat. No. 5,365,947 (“Adjustable Orthosis”), U.S. Pat. No. 5,285,773 (“Orthosis with Distraction through Range of Motion”), U.S. Pat. No. 5,213,095 (“Orthosis with Joint Distraction”), and U.S. Pat. No. 5,167,612 (“Adjustable Orthosis”), and U.S. Pat. No. 7,182,738 (“Patient monitoring apparatus and method for orthosis and other devices”), all to Bonutti and herein are expressly incorporated by reference in their entirety. It should be noted that the SPS protocol is disclosed in a number of the above-identified patents. It should be further noted that the mark STATIC PROGRESSIVE STRETCH COMPANY is a registered trademark of Joint Active Systems, Inc (Effingham, Ill.).
Another treatment protocol uses principles of creep to apply a constant force over variable displacement. In other words, techniques and devices utilizing principles of creep involve continued deformation with the application of a fixed load. For tissue, the deformation and elongation are continuous but slow (requiring hours to days to obtain plastic deformation), and the material is kept under a constant state of stress. Treatment methods such as traction therapy and dynamic splinting are based on the properties of creep.
One potential disadvantage of using a static load, however, is that the amount of force needed to effect tissue stretching or creep may change over time. For instance, while a 10 lb force may initially provide desirable results in the beginning of the treatment protocol, it may be insufficient after the tissue has begun to stretch. Likewise, the amount of force needed in the beginning of the treatment protocol may be too much force for use in later stages of the protocol.
Exemplary orthoses utilizing the creep protocol include U.S. Pat. Nos.; 5,167,612, 5,365,947, and 5,456,268 entitled “Adjustable Orthosis”, and U.S. Pat. No. 5,685,830 entitled “Adjustable Orthosis having one-piece connector section for flexing” all to Bonutti; U.S. Pat. No. 6,413,231, entitled “Device To Assist In Therapy Of Patient Who Has Limited Jaw Opening;” U.S. Pat. No. 5,645,521, entitled “Shoulder Physical Therapy Device;” U.S. Pat. No. 5,070,868, entitled “Adjustable Splint;” and U.S. Pat. No. 4,947,835, entitled “Adjustable splint assembly;” all to assigned to Dynasplint System Inc. and all of which herein are expressly incorporated by reference in their entirety. Another example of orthoses utilizing the creep protocol include U.S. Pat. No. 5,472, 410 to Hammersly, entitled “Adjustable Flexion and Extension Joint Orthoses,” and U.S. Pat. No. 5,437,619 to Malewicz et al., entitled “Range-of-Motion Splint with Eccentric Spring,” both of which are expressly incorporated by reference in their entirety.
In the past, treatment protocols and related devices utilized either stress relaxation or creep, but not both.